1. Field of Invention
The present invention relates to a liquid crystal display device and an electronic apparatus, and more specifically, to a transflective liquid crystal display device having both transmissive and reflective modes capable of obtaining a high contrast and a wide viewing angle.
2. Description of Related Art
A related art liquid crystal display device has been proposed where external light is used in a bright place similar to a reflective display and where an internal light source, such as a backlight, is used in a dark place to make the display visible. That is, this liquid crystal display device employs a display mode with both reflective and transmissive types, and is configured so as to reduce its power consumption by altering the display mode to one of the reflective and transmissive modes depending on the brightness of its surroundings, and can obtain a clear display even in dark surroundings, and is therefore suitable for a display for a portable apparatus. Hereinafter, such a liquid crystal display device is referred to as “a transflective liquid crystal display device” in the present specification.
As such a transflective liquid crystal display device, a related art liquid crystal display device has been proposed in which a liquid crystal layer is interposed between an upper substrate and a lower substrate and also a reflective film, in which an opening for light transmission is formed in a metal film, such as aluminum, is provided on the inner side of the lower substrate so as to function as a transflector. At this time, in the reflective mode, external light enters from the upper substrate and passes through a liquid crystal layer and then reflects on a reflective film of the inner side of the lower substrate and then passes through the liquid crystal layer again and then emits from the upper substrate, thereby contributing to display. However, in the transmissive mode, light from a backlight enters from a lower substrate and passes through a liquid crystal layer from the opening of the reflective film and then emits from the upper substrate to the outside, thereby contributing to the display. Therefore, in the forming region of the reflective film, the region in which an opening is formed is a transmissive display region, and the remaining region is a reflective display region.
However, the above transflective liquid crystal display device has a problem in that the viewing angle is narrow in the transmissive display. This is because the reflective display is to be performed only with a single sheet of polarizer which is provided on the observer side, since a transflector is provided on the inner plane of a liquid crystal cell so that parallax does not occur, thereby reducing the degree of freedom in the optical design. In order to address this problem, Jisaki et al. has proposed a novel transflective liquid crystal display device using a vertical alignment liquid crystal in “Development of transflective LCD for a high contrast and a wide viewing angle by using homeotropic alignment”, M. Jisaki et al., Asia Display/IDW'01, p. 133-136 (2001). Its characteristics are as follows:
(1) “A VA (Vertical Alignment) mode” has been employed where a liquid crystal with a negative dielectric anisotropy is aligned vertically to a substrate and is thrown down by the application of voltage.
(2) “A multigap structure” has been employed where a transmissive display region and a reflective display region are different in liquid crystal layer thickness (cell gap) from each other (see Japanese Unexamined Patent Application Publication No. 11-242226 in this regard).
(3) A transmissive display region is a regular octagon, and a protrusion is provided in the center of the transmissive display region on the counter substrate so that the liquid crystal is thrown down in eight directions within this region. In other words, “alignment division structure” has been employed.